Fiber optics are increasingly being utilized to carry optical energy from a variety of sources. In communications, fiber optics carry pulsed modulated signals originating from laser diodes. In fiber optic sensors, they carry intensity and wavelength information indicating the "sensed" substance. In industry, they are used to carry high power laser beams to cut and/or anneal materials. In laser surgery, fiber optics carry high power laser beams which cut and vaporize tissue.
In all cases, proper utilization of fiber optics requires precision optical alignment of the source of optical energy to the fiber optic. Depending upon the application, the light source may be a conventional laser, laser diode, LED, light source, or other fiber optic carrying optical energy. In many applications, the industry has standardized dimensional tolerances which permit easy alignment of the source to the fiber. This is true in the communications industry where the diode, fiber connections and components conform to precision standards. Such standards make connection and alignment of the source and fiber easy. Generally, however, other fields do not or cannot enjoy standardization between source and fiber. This is the case in the coupling of conventional lasers and fiber optics for industrial, medical and many sensing applications.
The alignment of non-standard components, or components in which the source can move from connection to connection (such as with articulating arms), has required costly time consuming methods and highly trained personnel. These techniques have required a stable optical bench or surface in which to establish reference points for optical instruments, sensitive and frequently costly detectors to measure the irradiance of the optical sources, apertures to block unwanted radiation, and precision manipulators to move components with respect to each other in order to obtain the desired alignment. In addition to the costly, time consuming and sensitive set up when such techniques are utilized, detectors and associated instrumentation frequently do not permit measuring the optical source at its point of focus. This occurs because of the physical size of the available detector. This is particularly true when the source focal point is located within an aligning collar. The fiber optic is held within the alignment pin. It is at the base of the alignment collar (where the beam is focused) that one wishes to place, and thus align, the optical fiber. Accordingly, there is a need for a device which will easily and inexpensively optically align the source and a fiber optic.
Solid state photo diodes are used almost exclusively for fiber optic power meter detectors. The small sensing area permits accurate locating of the optical beam. They are also used because the optical bandwidth is in the region of most popularly used fiber optics. Communication fiber optics and associated instruments have, and remain, the mainstay of the optical fiber industry. The optical wavelengths detected by solid state photo diodes include: silicon, 400-1100 microns; germanium 800-1800 microns; indium gallium arsenide, 900-1800 microns; mercury cadmium telluride, 1000-1300 microns. These detectors can typically measure total power in the range of one picowatt to tens of milliwatts. The active area of the detector can range from as small as 10.sup.-3 square millimeters for some mercury cadmium telluride detectors to fractions of a millimeter for germanium and silicon detectors to areas as large as several square centimeters for detector arrays.
Detectors for measuring high power and/or longer wavelength sources are generally in themselves not directly suitable for precision alignment of focused optical beams to fiber optics. Such transducers include thermopiles and pyroelectric detectors. These devices are generally larger, with active areas much greater than the beam and fiber diameters. Precision apertures which mask all but one small area of the detector must be used to restrict the active area of the detector. This clumsy, yet effective technique, is often employed for higher power and/or long wave length applications.